Gear motor for driving vehicle equipment with elimination of transmission line axial play

ABSTRACT

A reducing motor including a rotor with an armature shaft, a reducer housing ( 2 ) containing a gear wheel ( 3 ) engaging a worm on the shaft, and a shock absorber ( 5 ) housed in the gear wheel and rotationally integral therewith. The unitary shock absorber has circumferential notches ( 8 ) engageable both by radial flanges  87 ) on the gear wheel and by elements ( 10 ) for driving an output member ( 11 ), and chamfers ( 90 ) are provided on the edges of the notches to ensure gradual torque-dependent angular deflection of the shock absorber and make it easier to mount the same automatically on the hub of the gear wheel.

BACKGROUND OF THE INVENTION

The subject of the present invention is a geared motor unit,particularly for driving vehicle equipment such as window lifters,sunroofs, etc, and of the type comprising a rotor equipped with a rotorshaft, a reduction gearbox which contains a gearwheel in mesh with aworm belonging to the shaft and capable of driving an output member.

Geared motor units of this type are normally equipped with means foradjusting the axial play between one end of the rotor shaft and the wallof the box. This is because the axial play in the driveline mounted inthe geared motor unit is due to the combination of dimensional spreadson the various parts on assembly (shaft, endstop, box, etc.) which,placed end to end, are not as long as their housing.

Hitherto this axial play has been compensated for manually using a screwhoused in the end of the box facing the rotor shaft hole and which isimmobilized by an adhesive which at the same time provides sealing. Sucha method of adjustment is lengthy to perform, expensive, and increasesthe overall cost of manufacture of the geared motor unit.

It is also known practice (see U.S. Pat. No. 5,169,245) to achieveautomatic compensation for the axial play in the driveline of the gearedmotor unit using a coil spring resting in an axial housing of the end ofthe box, and a system of end stops designed to limit the compressiveaxial loading experienced by the coil spring to a predetermined value.This limitation is achieved by a shoulder on the inside of the wall ofthe box, and against which a piston inserted between the end of theshaft and the coil spring abuts.

Patent Abstracts of Japan Vol. 018 No. 297 of 7.6.1994 also discloses ageared motor unit in which an end stop, fixed by welding to one end ofthe box, eliminates any axial play between the rotor shaft and the wallof the box.

These devices for compensating for the axial play have a drawback whichlies in the fact that they are not able to eliminate the troublesomenoise of the shaft which is caused when it changes its direction ofrotation.

SUMMARY OF THE INVENTION

The object of the invention is therefore to eliminate this drawback byarranging the geared motor unit in such a way that these noises arecompletely eliminated.

According to the invention, the geared motor unit comprises means foreliminating, under a given compressive axial preload, any axial playbetween one end of the rotor shaft and the wall of the box.

According to one embodiment of the invention, the said means comprise aplug housed in the end of the box, and a piston inserted between theplug and the end of the shaft, the plug exerting the said compressiveaxial preload, set at the time of assembly, on the piston and on theshaft, and the box by melting the plastic of which the box is made intothe said roughnesses; this melting may be obtained, for example, using asonotrode, an ultrasonic-welding machine, or alternatively byhigh-frequency welding.

According to another possible embodiment of the invention, the gearedmotor unit comprises a metal plug mounted so that it can slide in anaxial housing formed in the wall of the box facing the end of the shaft;irregularities are arranged on the surface of this plug in contact withthe wall of the housing, and the plug is moved axially until it comesinto abutment against the end of the shaft under a given compressiveaxial preload thrust, then immobilized in this position so as toeliminate any shaft play.

This type of embodiment therefore has no piston, the plug alonefulfilling the function of plug and piston of the previous embodiment,and being immobilized in the desired position to exert appropriate axialthrust on the shaft.

The basic idea underlying the invention therefore consists ineliminating the axial play left in geared motor units of the state ofthe prior art and in doing so under a given compressive axial preload orthrust, for example of the order of 100 newtons.

BRIEF DESCRIPTION OF THE DRAWINGS

Other specific features and advantages of the invention will becomeapparent during the course of the description which will follow, whichis given with reference to the appended drawings which illustrate anumber of embodiments thereof by way of non-limiting examples.

FIG. 1 is a view in longitudinal elevation and part section of a gearedmotor unit for driving motor vehicle equipment, equipped with a devicefor eliminating the axial play in its driveline according to theinvention.

FIG. 2 is a view in cross section on 2/2 of FIG. 3, illustrating a firstembodiment of the gear motor unit according to the invention.

FIG. 3 is a view in partial longitudinal section showing one end of thegeared motor unit of FIG. 1 equipped with a device for eliminating theaxial play of the shaft according to a first embodiment of theinvention.

FIG. 4 is a view in partial longitudinal section similar to FIG. 3illustrating a second embodiment of the device for eliminating axialplay in the geared motor unit according to the invention.

FIG. 5 is a view in side elevation of an alternative form of the pistonof FIGS. 3 and 4.

FIGS. 6, 7 and 8 are views similar to FIG. 3 of three other embodimentsof the device for eliminating axial play at which the invention isintended.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The geared motor unit 1 illustrated in FIG. 1 is intended, inparticular, for driving vehicle equipment such as electric windowlifters.

It comprises, housed inside a casing 2, a stator 3 which can be poweredby electrical connections 4 in the known way, a rotor 5 equipped with arotor shaft 6, the ends of which are mounted in rolling bearings 7, 8.This rotor shaft carries a worm 9 in mesh with a gearwheel 11 capable ofdriving an output member 12 which itself drives the equipment associatedwith the geared motor unit, for example a window lifter, a sunroof, etc.

The end 6 a of the rotor shaft 6 passing through the bearing 7, locatednear the worm 9 collaborates with a device 12 making it possible, undera given compressive axial preload F (FIG. 3) to eliminate any axial playbetween the end 6 a of the shaft 6 and the wall 13 of the reductiongearbox 14.

In the embodiment illustrated in FIGS. 2 and 3, the means whichconstitute the device 12 comprise a plug 15 made of an elastic materialsuch as an elastomer, arranged in a terminal housing 17 at the end ofthe wall 13 and projecting axially from this housing 17, towards the end6 a of the shaft 6. The device 12 also comprises a piston 18 insertedbetween the plug 15 and the end 6 a of the shaft 6. Arranged on theperipheral surface of the piston 18, in contact with the interior wall13 a of the end 13 of the box 14 are irregularities such as circulargrooves 19 or, alternatively, a screw thread, notching, axial grooves,knurling, etc., the piston 18 being made of metal, whereas the box 14 ismade of plastic.

When the geared motor unit is assembled, the piston 18 is pressedagainst the plug 15, precompressing it so that it exerts a compressiveaxial preload thrust F of an appropriate value, such as about 100newtons, on the piston 18 and on the end 6 a of the shaft 6.

Once this compressive preload F has been set to the desired value, thepiston 18 is immobilized in the axial position that corresponds to thesaid compressive preload of the plug 15, and this is done by heating theplastic of the end 13 of the box 14 facing the surface irregularities ofthe piston 18, so that the molten plastic fills its grooves or channels19. Subsequent solidification of the plastic by cooling fixes the piston18 permanently in this position at the end 13 of the box 14. Thismelting of the plastic may be brought about by appropriate means, notdepicted, such as an ultrasound generator or using high-frequencywelding.

Once the piston 18 has been secured to the box 14 in this way, changesin direction of rotation of the rotor shaft 6 can no longer cause thisshaft to move axially and therefore can no longer generate troublesomenoise.

In the second embodiment illustrated in FIG. 4, the device 21 comprisesa piston 22, the peripheral surface irregularities of which, in contactwith the interior wall 13 a, consist of two circular channels 23 formedon the edges of the piston 22 and separated by a cylindrical region 14.Correspondingly, at least one duct 25 is arranged to the side of thepiston 22 in the wall 13 of the box 14 and opens into an annular chamber26 in the wall 13, this chamber 26 itself opening onto the circulargrooves 23.

This device 21 for eliminating axial play in the shaft 6 is adjusted asfollows: first of all, the compressive axial preload F of the plug 15 isadjusted to the desired value, so that the piston 22 is positionedexactly at the appropriate axial location, opposite the chamber 26.Next, a liquid adhesive is injected into the lateral duct 25 so that itfills the chamber 26 and the channels 23. The pressure with which theliquid adhesive is injected is arbitrary. After hardening, the adhesiveentirely fills the channels 23, the chamber 26 and the duct 25 thushermetically sealed and immobilizes the piston 22 with respect to thewall 13 of the box 14. As before, the piston 22 eliminates any axialplay of the rotor shaft 6 and therefore any parasitic noise as the shaftchanges direction of rotation.

In the alternative form of FIG. 5, the piston 27 has three circularchannels 28, the central cylindrical region 24 having been omitted. Inother respects, the use of the piston 27 is entirely similar to that ofthe piston 22.

In the alternative form of FIG. 6, the device 29 for eliminating theaxial play of the shaft 6 comprises a piston 27 with a number ofcircular channels 28 and a peripheral counterbore 31 which is shaped soas to delimit, facing the channels 28, complementary channels 32 whichare formed in the wall 13 of the box 14. This counterbore 31 and thegrooves 28 can be filled with liquid adhesive via the side duct 25, thepiston 27 being immobilized by the solidified adhesive.

FIG. 7 illustrates a fourth embodiment of the invention in which thedevice 33 for eliminating the play of the shaft 6 comprises a metal plug34 with a diameter greater than the diameter of the axial housing 35formed in the wall 13 of the reduction gearbox 14 facing the end 6 a ofthe shaft 6. There are irregularities 36 on the surface of this plug 34in contact with the wall of the housing 35, for example knurling asdepicted, or alternatively notching, etc.

The plug 34 is moved axially in the housing 35 by melting the plastic ofthe wall 13 using means which are known and have not been depicted,until this plug comes into abutment against the end 6 a of the shaft 6with a given compressive axial preload thrust F (for example 100newtons). The position of the plug 34 before it is introduced isdepicted in chain line in FIG. 7.

The plug 34 is positioned axially at the precise desired location inorder to place the shaft 6 under compressive preload using anultrasonic-welding machine which causes the plastic of the wall 13 ofthe housing 35 to melt into the surface irregularities 36. This machineis associated with a thrusting ram which defines the amount ofcompressive preload on the driveline. Immobilization is achieved by thehardening of the plastic when the ultrasonic transducer has been shutdown.

FIG. 8 illustrates a fifth embodiment which constitutes an alternativeform of FIG. 7, in which the plug 37, preferably made of metal, has asmooth surface and is immobilized in its axial position, compressedagainst the end 6 a of the shaft 6, by solidified adhesive 38. Thelatter is injected in the liquid state through an axial nozzle 39 formedin the wall 13 of the box 14 and which opens into the housing 35. Theliquid adhesive is injected under a given pressure and fills that partof the housing 35 which is located behind the plug 37.

Use is made, for example, of a hot-melt adhesive, which melts at atemperature lower than the melting point of the plastic of which the box14 is made (200° C.) at low pressure.

By way of an unlimiting numerical example, if the axial thrust F is 100newtons, and the cross-sectional area S of the plug 37 is equal to 0.5cm², the pressure with which the adhesive is injected must be equal to20 bar.

Injecting a plastic identical to that of the box 14 is difficult toenvisage because it would have to be done at high pressure, which wouldentail a plug 37 of very low cross section.

The invention is not restricted to the embodiments described and itsexecution may be varied in a number of ways. Thus, the embodiment ofFIG. 8 could be modified by completely opening the housing 35 to theoutside of the box 14 as depicted in FIG. 7, by arranging surfaceirregularities (grooves, knurling, etc.) on the surface of the plug 37and by forming a side nozzle and a counterbore in the wall 13 of the box14 so that liquid adhesive can be injected against the periphery of theplug 37 once the plug has been correctly axially positioned at thedesired location. To perform this positioning operation, the plug 37 ispushed by an exterior precompression ram and immobilized by injectingadhesive into its grooves, via the counterbore in the box.

The foregoing description is only exemplary of the principles of theinvention. Many modifications and variations of the present inventionare possible in light of the above teachings. The preferred embodimentsof this invention have been disclosed, however, so that one of ordinaryskill in the art would recognize that certain modifications would comewithin the scope of this invention. It is, therefore, to be understoodthat within the scope of the appended claims, the invention may bepracticed otherwise than as specially described. For that reason thefollowing claims should be studied to determine the true scope andcontent of this invention.

What is claimed is:
 1. A geared motor unit, for driving vehicleequipment, comprising: a rotor equipped with a rotor shaft, a reductiongearbox which contains a gearwheel in mesh with a worm belonging to theshaft and capable of driving an output member, and a device foreliminating, under a given compressive axial preload, axial play betweenone end of the rotor shaft and a wall of the box, wherein the deviceincludes a plug housed in an end of the box, and a piston insertedbetween the plug and the end of the shaft, the plug exerting thecompressive axial preload on the piston and on the shaft, and animmobilization system for immobilizing the piston in the axial positionthat corresponds to the compressive preload.
 2. The geared motor unitaccording to claim 1, wherein the immobilization system for immobilizingthe piston in the axial position include irregularities formed on asurface of the piston in contact with the wall of the box, the pistonbeing made of metal and the box being made of plastic, and the piston isimmobilized with respect to the wall of the box by melting the box intothe irregularities.
 3. The gear motor unit according to claim 2, whereinthe irregularities are grooves.
 4. The gear motor unit according toclaim 2, wherein the box is melted into the irregularities by usingultrasound.
 5. The gear motor unit according to claim 2, wherein the boxis melted into the irregularities by using high-frequency welding. 6.The geared motor unit according to claim 1, wherein the immobilizationsystem for immobilizing the piston includes surface irregularitiesformed on the surface of the piston in contact with the wall of the box,at least one duct arranged to a side of the piston in the wall of thebox and opening into a chamber of the wall, and hardened adhesiveinjected in a liquid state through the duct into the surfaceirregularities.
 7. A geared motor unit, for driving vehicle equipment,comprising: a rotor equipped with a rotor shaft, a reduction gearboxwhich contains a gearwheel in mesh with a worm belonging to the shaftand capable of driving an output member, and a device for eliminating,under a given compressive axial preload, axial play between one end ofthe rotor shaft and a wall of the box, wherein the device includes aplug housed in an end of the box, and a piston inserted between the plugand the end of the shaft, the plug exerting the compressive axialpreload on the piston and on the shaft, and an immobilization system forimmobilizing the piston in the axial position that corresponds to thecompressive preload including irregularities formed on a surface of thepiston in contact with the wall of the box, and a securing materialenters the irregularities to immobilize the piston with respect to thewall of the box.
 8. The geared motor unit according to claim 7, whereinthe piston is made of metal and the box is made of plastic, and thepiston is immobilized with respect to the wall of the box by melting thebox, the melted plastic of the box providing the securing material.
 9. Ageared motor unit, for driving vehicle equipment, comprising: a rotorequipped with a rotor shaft, a reduction gearbox which contains agearwheel in mesh with a worn belonging to the shaft and capable ofdriving an output member, and a device for eliminating, under a givencompressive axial preload, axial play between one end of the rotor shaftand a wall of the box, wherein the device includes a plug housed in anend of the box, and a piston inserted between the plug and the end ofthe shaft, the plug exerting the compressive axial preload on the pistonand on the shaft, and an immobilization system for immobilizing thepiston in the axial position that corresponds to the compressivepreload, wherein the immobilization system for immobilizing the pistonincludes surface irregularities formed on the surface of the piston incontact with the wall of the box, at least one duct arranged to a sideof the piston in the wall of the box and opening into a chamber of thewall and hardened adhesive injected in a liquid state through the ductinto the surface irregularities, and the surface irregularities arechannels arranged on a peripheral surface of the piston in contact withthe wall of the box.
 10. A geared motor unit, for driving vehicleequipment, comprising: a rotor equipped with a rotor shaft, a reductiongearbox which contains a gearwheel in mesh with a worm belonging to theshaft and capable of driving an output member, and a device foreliminating, under a given compressive axial preload, axial play betweenone end of the rotor shaft and a wall of the box, wherein the deviceincludes a plug housed in an end of the box, and a piston insertedbetween the plug and the end of the shaft, the plug exerting thecompressive axial preload on the piston and on the shaft, and animmobilization system for immobilizing the piston in the axial positionthat corresponds to the compressive preload, wherein the immobilizationsystem for immobilizing the piston includes surface irregularitiesformed on the surface of the piston in contact with the wall of the box,at least one duct arranged to a side of the piston in the wall of thebox and opening into a chamber of the wall, and hardened adhesiveinjected in a liquid state through the duct into the surfaceirregularities, and a nozzle opens into a counterbore and complementarychannels are formed in the wall of the box around the piston and thehardened adhesive is injected into the surface irregularities and thecomplementary channels.
 11. A geared motor unit, for driving vehicleequipment, comprising: a rotor equipped with a rotor shaft, a reductiongearbox which contains a gearwheel in mesh with a worm belonging to theshaft and capable of driving an output member, and a device foreliminating, under a given compressive axial preload, axial play betweenone end of the rotor shaft and a wall of the box, wherein the deviceincludes a plug housed in an end of the box, and a piston insertedbetween the plug and the end of the shaft, the plug exerting thecompressive axial preload on the piston and on the shaft, and animmobilization system for immobilizing the piston in the axial positionthat corresponds to the compressive preload including irregularitiesformed on a surface of the piston in contact with the wall of the box,and a securing material enters the irregularities to immobilize thepiston with respect to the wall of the box, and at least one duct isarranged to a side of the piston in the wall of the box and opens into achamber of the wall, and the securing material is a hardened adhesiveinjected in a liquid state through the duct.